Sideboard



FIG. 1 is a right front perspective view of a sideboard showing my new design;

FIG. 2 is a front elevational view thereof; and,

FIG. 3 is a side elevational view, the opposite side being a mirror image thereof.

The views of the sideboard not shown form no part of the claimed design. The broken lines depicting hardware and doors represent environmental elements only and form no part of the claimed design. 

The ornamental design for a sideboard, as shown and described. 